Merge pull request #17370 from zerafachris/fix/item-update-null-optional-fields

fix: don't throw ArgumentNullException on partial UpdateItem payloads (#17366)

tests/Jellyfin.Api.Tests/Controllers/ItemUpdateControllerTests.cs

@@ -0,0 +1,77 @@
+using System;
+using System.Threading.Tasks;
+using Jellyfin.Api.Controllers;
+using MediaBrowser.Controller.Configuration;
+using MediaBrowser.Controller.Entities;
+using MediaBrowser.Controller.Entities.Movies;
+using MediaBrowser.Controller.Library;
+using MediaBrowser.Controller.Providers;
+using MediaBrowser.Model.Dto;
+using MediaBrowser.Model.Globalization;
+using MediaBrowser.Model.IO;
+using Moq;
+using Xunit;
+
+namespace Jellyfin.Api.Tests.Controllers;
+
+public class ItemUpdateControllerTests
+{
+    private readonly ItemUpdateController _subject;
+
+    public ItemUpdateControllerTests()
+    {
+        _subject = new ItemUpdateController(
+            Mock.Of<IFileSystem>(),
+            Mock.Of<ILibraryManager>(),
+            Mock.Of<IProviderManager>(),
+            Mock.Of<ILocalizationManager>(),
+            Mock.Of<IServerConfigurationManager>());
+    }
+
+    [Fact]
+    public async Task UpdateItem_WhenOnlyTagsFieldSupplied_DoesNotThrowAndAppliesTags()
+    {
+        // Regression test for https://github.com/jellyfin/jellyfin/issues/17366
+        // A partial update payload that only sets "Tags" leaves every other
+        // BaseItemDto collection property null (they have no default
+        // initializer). Genres and ProviderIds used to be fed straight into
+        // Distinct()/ToList() without a null check, so this call used to throw
+        // ArgumentNullException before the fix below was applied.
+        var movie = new Movie();
+        var request = new BaseItemDto
+        {
+            Tags = new[] { "new-tag-1", "new-tag-2" }
+        };
+
+        await InvokeUpdateItem(request, movie);
+
+        Assert.Equal(new[] { "new-tag-1", "new-tag-2" }, movie.Tags);
+        Assert.Empty(movie.Genres);
+        Assert.Empty(movie.ProviderIds);
+    }
+
+    [Fact]
+    public async Task UpdateItem_WhenGenresAndProviderIdsOmitted_LeavesExistingValuesUnchanged()
+    {
+        var movie = new Movie
+        {
+            Genres = new[] { "Action" }
+        };
+        movie.ProviderIds["Imdb"] = "tt1234567";
+
+        var request = new BaseItemDto
+        {
+            Tags = Array.Empty<string>()
+        };
+
+        await InvokeUpdateItem(request, movie);
+
+        Assert.Equal(new[] { "Action" }, movie.Genres);
+        Assert.Equal("tt1234567", movie.ProviderIds["Imdb"]);
+    }
+
+    private Task InvokeUpdateItem(BaseItemDto request, BaseItem item)
+    {
+        return _subject.UpdateItem(request, item);
+    }
+}